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Title: The c/a Ratio in Quenched Fe-C and Fe-N steels - a Heuristic Story

Abstract

The body-centered tetragonal (BCT) structure in quenched Fe-C steels is usually illustrated to show a linear change in the c and a axes with an increase in carbon content from 0 to 1.4%C. The work of Campbell and Fink, however, shows that this continuous linear relationship is not correct. Rather, it was shown that the body-centered-cubic (BCC) structure is the stable structure from 0 to 0.6 wt%C with the c/a ratio equal to unity. An abrupt change in the c/a ratio to 1.02 occurs at 0.6 wt%C. The BCT structure forms, and the c/a ratio increases with further increase in carbon content. An identical observation is noted in quenched Fe-N steels. This discontinuity is explained by a change in the transformation process. It is proposed that a two-step transformation process occurs in the low carbon region, with the FCC first transforming to HCP and then from HCP to BCC. In the high carbon region, the FCC structure transforms to the BCT structure. The results are explained with the Engel-Brewer theory of valence and crystal structure of the elements. An understanding of the strength of quenched iron-carbon steels plays a key role in the proposed explanation of the c/a anomaly basedmore » on interstitial solutes and precipitates.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
893988
Report Number(s):
UCRL-CONF-218604
TRN: US200701%%86
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: Presented at: THERMEC 2006, Vancouver, Canada, Jul 04 - Jul 08, 2006
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BCC LATTICES; CARBON; CRYSTAL STRUCTURE; INTERSTITIALS; SOLUTES; STEELS; TRANSFORMATIONS; VALENCE

Citation Formats

Sherby, O, Wadsworth, J, Lesuer, D, and Syn, C. The c/a Ratio in Quenched Fe-C and Fe-N steels - a Heuristic Story. United States: N. p., 2006. Web.
Sherby, O, Wadsworth, J, Lesuer, D, & Syn, C. The c/a Ratio in Quenched Fe-C and Fe-N steels - a Heuristic Story. United States.
Sherby, O, Wadsworth, J, Lesuer, D, and Syn, C. Tue . "The c/a Ratio in Quenched Fe-C and Fe-N steels - a Heuristic Story". United States. doi:. https://www.osti.gov/servlets/purl/893988.
@article{osti_893988,
title = {The c/a Ratio in Quenched Fe-C and Fe-N steels - a Heuristic Story},
author = {Sherby, O and Wadsworth, J and Lesuer, D and Syn, C},
abstractNote = {The body-centered tetragonal (BCT) structure in quenched Fe-C steels is usually illustrated to show a linear change in the c and a axes with an increase in carbon content from 0 to 1.4%C. The work of Campbell and Fink, however, shows that this continuous linear relationship is not correct. Rather, it was shown that the body-centered-cubic (BCC) structure is the stable structure from 0 to 0.6 wt%C with the c/a ratio equal to unity. An abrupt change in the c/a ratio to 1.02 occurs at 0.6 wt%C. The BCT structure forms, and the c/a ratio increases with further increase in carbon content. An identical observation is noted in quenched Fe-N steels. This discontinuity is explained by a change in the transformation process. It is proposed that a two-step transformation process occurs in the low carbon region, with the FCC first transforming to HCP and then from HCP to BCC. In the high carbon region, the FCC structure transforms to the BCT structure. The results are explained with the Engel-Brewer theory of valence and crystal structure of the elements. An understanding of the strength of quenched iron-carbon steels plays a key role in the proposed explanation of the c/a anomaly based on interstitial solutes and precipitates.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jan 31 00:00:00 EST 2006},
month = {Tue Jan 31 00:00:00 EST 2006}
}

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